CN117344213A - 900 MPa-level ultralow-carbon medium-manganese high-strength hot rolled steel plate and manufacturing method thereof - Google Patents
900 MPa-level ultralow-carbon medium-manganese high-strength hot rolled steel plate and manufacturing method thereof Download PDFInfo
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 158
- 239000010959 steel Substances 0.000 title claims abstract description 158
- 229910052799 carbon Inorganic materials 0.000 title claims abstract description 42
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 34
- 239000011572 manganese Substances 0.000 title claims abstract description 33
- 229910052748 manganese Inorganic materials 0.000 title claims abstract description 29
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 30
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 claims abstract description 21
- 239000012535 impurity Substances 0.000 claims abstract description 7
- 239000000126 substance Substances 0.000 claims abstract description 6
- 229910001566 austenite Inorganic materials 0.000 claims description 38
- 238000001816 cooling Methods 0.000 claims description 37
- 238000005096 rolling process Methods 0.000 claims description 31
- 238000000034 method Methods 0.000 claims description 27
- 230000008569 process Effects 0.000 claims description 25
- 229910000859 α-Fe Inorganic materials 0.000 claims description 21
- 229910001563 bainite Inorganic materials 0.000 claims description 17
- 238000010438 heat treatment Methods 0.000 claims description 15
- 238000009749 continuous casting Methods 0.000 claims description 7
- 238000003723 Smelting Methods 0.000 claims description 6
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 6
- 238000005266 casting Methods 0.000 claims description 5
- 230000000717 retained effect Effects 0.000 claims 1
- 230000002829 reductive effect Effects 0.000 description 16
- 230000009466 transformation Effects 0.000 description 16
- 239000010955 niobium Substances 0.000 description 8
- 230000006911 nucleation Effects 0.000 description 8
- 238000010899 nucleation Methods 0.000 description 8
- 238000005728 strengthening Methods 0.000 description 8
- 229910045601 alloy Inorganic materials 0.000 description 7
- 239000000956 alloy Substances 0.000 description 7
- 230000000694 effects Effects 0.000 description 7
- 238000005496 tempering Methods 0.000 description 7
- 229910052782 aluminium Inorganic materials 0.000 description 6
- 239000010936 titanium Substances 0.000 description 6
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 5
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 5
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 5
- 238000005516 engineering process Methods 0.000 description 5
- 229910052750 molybdenum Inorganic materials 0.000 description 5
- 239000011733 molybdenum Substances 0.000 description 5
- 229910052758 niobium Inorganic materials 0.000 description 5
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 description 5
- 238000001556 precipitation Methods 0.000 description 5
- 238000009792 diffusion process Methods 0.000 description 4
- 229910000510 noble metal Inorganic materials 0.000 description 4
- 239000006104 solid solution Substances 0.000 description 4
- 229910000617 Mangalloy Inorganic materials 0.000 description 3
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 3
- 230000008901 benefit Effects 0.000 description 3
- 229910052804 chromium Inorganic materials 0.000 description 3
- 239000011651 chromium Substances 0.000 description 3
- 230000006835 compression Effects 0.000 description 3
- 238000007906 compression Methods 0.000 description 3
- 238000010791 quenching Methods 0.000 description 3
- 230000000171 quenching effect Effects 0.000 description 3
- 229910052710 silicon Inorganic materials 0.000 description 3
- 239000010703 silicon Substances 0.000 description 3
- 238000004781 supercooling Methods 0.000 description 3
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 2
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 125000004432 carbon atom Chemical group C* 0.000 description 2
- 229910001567 cementite Inorganic materials 0.000 description 2
- 238000005520 cutting process Methods 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- KSOKAHYVTMZFBJ-UHFFFAOYSA-N iron;methane Chemical compound C.[Fe].[Fe].[Fe] KSOKAHYVTMZFBJ-UHFFFAOYSA-N 0.000 description 2
- 229910000734 martensite Inorganic materials 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 239000011159 matrix material Substances 0.000 description 2
- 238000001953 recrystallisation Methods 0.000 description 2
- 238000007670 refining Methods 0.000 description 2
- 238000010583 slow cooling Methods 0.000 description 2
- 230000000087 stabilizing effect Effects 0.000 description 2
- 229910052719 titanium Inorganic materials 0.000 description 2
- 238000003466 welding Methods 0.000 description 2
- 229910001339 C alloy Inorganic materials 0.000 description 1
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 1
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 125000004429 atom Chemical group 0.000 description 1
- 238000005452 bending Methods 0.000 description 1
- FFBHFFJDDLITSX-UHFFFAOYSA-N benzyl N-[2-hydroxy-4-(3-oxomorpholin-4-yl)phenyl]carbamate Chemical compound OC1=C(NC(=O)OCC2=CC=CC=C2)C=CC(=C1)N1CCOCC1=O FFBHFFJDDLITSX-UHFFFAOYSA-N 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 238000005097 cold rolling Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000005261 decarburization Methods 0.000 description 1
- 230000000593 degrading effect Effects 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 230000006698 induction Effects 0.000 description 1
- 230000002401 inhibitory effect Effects 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 230000000670 limiting effect Effects 0.000 description 1
- WPBNNNQJVZRUHP-UHFFFAOYSA-L manganese(2+);methyl n-[[2-(methoxycarbonylcarbamothioylamino)phenyl]carbamothioyl]carbamate;n-[2-(sulfidocarbothioylamino)ethyl]carbamodithioate Chemical compound [Mn+2].[S-]C(=S)NCCNC([S-])=S.COC(=O)NC(=S)NC1=CC=CC=C1NC(=S)NC(=O)OC WPBNNNQJVZRUHP-UHFFFAOYSA-L 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 229910001562 pearlite Inorganic materials 0.000 description 1
- 230000005501 phase interface Effects 0.000 description 1
- 230000002441 reversible effect Effects 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
Classifications
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
- C21D8/0226—Hot rolling
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
- C21D8/0263—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment following hot rolling
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/001—Austenite
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/002—Bainite
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/005—Ferrite
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Heat Treatment Of Steel (AREA)
Abstract
A900 MPa-level ultra-low carbon medium manganese high-strength hot rolled steel plate and a manufacturing method thereof are provided, wherein the chemical components in percentage by weight are as follows: c: 0.06-0.12%, si:0.6 to 1.6 percent, mn: 4-6%, al:0 to 0.2 percent, P: < 0.01%, S: < 0.002%, nb:0.01 to 0.08 percent, ti:0.05 to 0.15 percent, mo:0.1 to 0.4 percent, and the balance of Fe and unavoidable impurities; and, need satisfy simultaneously: when C is less than or equal to 0.1 percent, mn:4 to 6 percent; when C is more than 0.1%, mn is less than or equal to 5%. The yield strength is more than or equal to 880MPa at room temperature, the tensile strength is more than or equal to 1200MPa, the yield ratio is less than 0.75, the elongation reaches more than 16%, and the Charpy impact energy at room temperature is more than or equal to 60J; and has low cost and simple production process.
Description
Technical Field
The invention relates to the technical field of steel for engineering machinery, in particular to a 900 MPa-level ultralow-carbon medium-manganese high-strength hot rolled steel plate and a manufacturing method thereof.
Background
In the requirements of thick plate performance in the fields of steel for engineering machinery and the like, there is no clear limitation on the carbon content and carbon equivalent of the steel plate due to the requirement of weldability of the steel plate, but in the process of developing the steel plate, the lower carbon equivalent is always a target pursued by the developer. Because the carbon content in the steel is low, the strength of the steel plate is insufficient, a certain amount of noble metal elements such as Cr, ni, mo and the like are often added to improve the strength of the steel plate, and meanwhile, the impact toughness of the steel plate is considered to produce the steel plate by adopting processes such as controlled rolling, controlled cooling and the like, so that the production cost of the steel plate is greatly increased.
At present, the medium manganese steel product is widely applied to the manufacture of automobile plates, and through a proper heat treatment process, a steel plate matrix structure can be a multiphase structure formed by mixing bainite, martensite and residual austenite, so that the medium manganese steel plate can obtain high strength, and meanwhile, the steel plate has good plastic toughness. However, a reasonable off-line heat treatment process is usually required to be matched, and the tissues with different proportions are obtained in the steel, so that the effect of adjusting the mechanical properties of the steel plate is achieved. In addition, steel for automobiles is mostly a thin-gauge material, and in the actual production process, the steel plate is produced in a cold rolling mode due to large compression ratio or brittleness, and the crystal grains of the steel plate are sufficiently refined in the deformation process, so that the strength of the steel plate is improved.
For the high-strength steel of the medium plate, because the thickness of the steel plate is larger, in the actual production process, the rolling compression ratio is small, and the steel plate is usually produced in a mode of controlling rolling and cooling, so that the temperature is required to be controlled in the production process or the steel plate is required to be subjected to subsequent tempering heat treatment after being rolled, the production efficiency is reduced, and the off-line heat treatment also can bring about the improvement of the production cost. Meanwhile, the addition of noble metal elements such as Cr, ni, mo and the like also increases the cost of alloy elements of the steel.
For example, chinese patent CN110952020A discloses an economic 900MPa grade super high strength steel plate and a production method thereof, wherein the steel plate comprises the following components in percentage: c:0.155 to 0.175 percent, si:0.1 to 0.3 percent, mn:1.20 to 1.40 percent, P is less than or equal to 0.013 percent, S is less than or equal to 0.003 percent, nb:0.020 to 0.030 percent, ti:0.010 to 0.020%, cr:0.20 to 0.40 percent, mo:0.30 to 0.40 percent, B:0.0010 to 0.0020 percent, als: 0.015-0.050%, the balance being iron and unavoidable impurities, heating and preserving heat of the continuous casting blank at 1230-1270 ℃, then carrying out two-stage rolling, rough rolling at 1050-1100 ℃, finishing rolling after finishing rolling at 3 times thickness of the finished steel plate, finishing rolling at 800-840 ℃, and cooling to 650-700 ℃ in an accelerated way after rolling, and cooling to room temperature. Quenching the rolled steel plate at 880-910 ℃, and tempering and preserving heat at 540-560 ℃.
For another example, chinese patent CN106319350a discloses a rolling and heat treatment production method of a high-strength steel with a yield strength of 900MPa, and the steel plate comprises the following components: c:0.10 to 0.20 percent, si:0.10 to 0.50 percent, mn:1.00 to 1.60 percent, P is less than or equal to 0.015 percent, S is less than or equal to 0.005 percent, cr:0.10 to 0.50 percent, mo:0.20 to 0.60 percent, nb:0.015 to 0.055 percent, V:0.020 to 0.060 percent, ti:0.003 to 0.04 percent of Al:0.02 to 0.07 percent, B:0.0006 to 0.0025 percent, and the balance of Fe and unavoidable impurities. The production method of the steel plate comprises the steps of heating and rolling a continuous casting blank at 1100-1250 ℃, cooling the steel plate to 500-700 ℃ in a laminar cooling mode at the final rolling temperature of 820-880 ℃ and coiling in a laminar cooling mode at the speed of 10-25 ℃ per second, transversely cutting and straightening a steel coil with the temperature lower than 80 ℃ to form the steel plate, quenching at 850-950 ℃ and tempering at 500-700 ℃.
In view of the above-mentioned patent situation of high strength steel sheet, most 900MPa grade steel sheet is required to be controlled rolled or subsequently subjected to tempering heat treatment, and low cost ultra low carbon high strength steel sheet manufactured by controlled rolling and controlled cooling has not been reported yet.
Disclosure of Invention
The invention aims to provide a 900 MPa-grade ultralow-carbon medium-manganese high-strength hot rolled steel plate and a manufacturing method thereof, wherein the yield strength is more than or equal to 880MPa, the tensile strength is more than or equal to 1200MPa, the yield ratio is less than 0.75, the elongation reaches more than 16%, and the Charpy impact energy at room temperature is more than or equal to 60J; and the alloy has low cost and simple production process, and has remarkable comprehensive advantages compared with other medium-high alloy high-strength steel.
In order to achieve the above purpose, the technical scheme of the invention is as follows:
a900 MPa-level ultra-low carbon medium-manganese high-strength hot rolled steel plate comprises the following chemical components in percentage by weight: c: 0.06-0.12%, si:0.6 to 1.6 percent, mn: 4-6%, al:0 to 0.2 percent, P: < 0.01%, S: < 0.002%, nb:0.01 to 0.08 percent, ti:0.05 to 0.15 percent, mo:0.1 to 0.4 percent, and the balance of Fe and unavoidable impurities; and, need satisfy simultaneously:
when C is less than or equal to 0.1 percent, mn:4 to 6 percent;
when C is more than 0.1%, mn is less than or equal to 5%.
The balance being Fe and other unavoidable impurities.
The microstructure of the hot rolled steel plate is 10-15% of fine grain ferrite, 80-85% of lath bainite and a small amount of residual austenite.
In the component design of the 900 MPa-level ultra-low carbon medium manganese high-strength hot rolled steel plate, the following components are adopted:
carbon C: the strength of the material can be ensured, and the strength of the steel plate is obviously improved along with the increase of the carbon content. However, too high a carbon content may cause a decrease in toughness of the steel sheet, and at the same time, increase weld crack sensitivity of the steel sheet, and decrease welding performance of the steel sheet. The invention adopts the design of ultra-low carbon, and the ferrite transformation starting temperature and the ferrite transformation ending temperature of the steel plate are kept in a wider temperature range through the interaction with Mn element, so that the operability of field implementation is improved. When the carbon content exceeds 0.1%, in order to ensure the range of the ferrite transformation starting and ending temperatures of the steel plate, the content of Mn element needs to be strictly controlled to be not more than 5%, otherwise, a water cooling process window is reduced, and the site control implementation is not facilitated; meanwhile, when the carbon content exceeds 0.12%, A is brought about 1 The significant increase in temperature, the process availability is lost. Therefore, the invention controls the content of C to be 0.06-0.12%.
Silicon Si: silicon has the function of solid solution strengthening, can improve the corrosion resistance and high-temperature oxidation resistance of steel, and the addition of Si can effectively improve the elastic modulus of the steel plate; however, too high a content may result in serious decarburization of the steel surface, degrading the welding performance. In addition, after the steel is cooled to the low temperature of 400 ℃ or below, silicon and aluminum in the steel can effectively play a role in inhibiting cementite precipitation, so that more carbon in the steel is utilized to stabilize unconverted austenite, and the stability of the austenite is further improved. Therefore, the Si content is limited to 0.6-1.6%.
Manganese Mn: manganese is a main element for stabilizing austenite in steel, is a key element of the invention, can obviously shift the CCT curve of the steel to the right, reduce the critical cooling speed of the steel, improve the hardenability of the steel plate, reduce the start and end temperatures of eutectoid transformation of the steel, refine the ferrite pearlite structure in the steel and ensure the steel plate to have higher strength. In the invention, the manganese content is strictly matched with the carbon element content, and when the carbon content is less than 0.1%, the eutectoid transformation ending temperature of the steel is continuously reduced along with the increase of the manganese element, so that the control effect on the process is not great. However, when the carbon content in the steel is more than 0.1%, the manganese content in the steel cannot exceed 5%, otherwise the start and end temperature ranges of severe compression eutectoid transformation may result in that the ferrite content in the steel according to the present invention cannot be significantly reduced, and the ductility and toughness of the steel sheet are reduced. In addition, manganese is also a solid solution strengthening element in steel, and can effectively improve the strength of the steel plate. However, too much manganese content also results in an increase in the carbon equivalent of the steel sheet, reducing the weldability of the steel sheet, and at the same time, leading to an increase in cost. Therefore, the carbon content of the present invention is controlled to 4 to 6%.
Aluminum Al: the aluminum can effectively prevent cementite from forming in steel, is beneficial to solid solution of carbon in austenite, improves the stability of austenite in the cooling process, and is greatly beneficial to improving the toughness of the steel plate. However, if the aluminum content in the steel is too high, the difficulty of smelting and pouring the steel is increased, the manufacturing cost is increased, and excessive oxide is formed to deteriorate the quality of the steel plate. Therefore, the present invention defines an Al content of 0 to 0.2%.
Titanium Ti: titanium is a strong carbide forming element, and TiN can be formed in steel, and acts as particles for austenite nucleation, thereby serving to refine austenite grains. The addition of trace Ti in the invention mainly plays a role in refining austenite grains, if the content of Ti is too high, tiC is precipitated, C in steel is consumed, the solid solubility of C in austenite is reduced, and the stability of austenite is reduced. Therefore, the Ti content is controlled to be 0.05-0.15%.
Niobium Nb: niobium is a strong carbide forming element, and in the process of high-temperature rolling deformation in steel, the niobium plays a role in refining rolled austenite grains through deformation induction precipitation, and meanwhile, the precipitated carbide pinning dislocation can play a role in precipitation strengthening. Too low a Nb content, the effects of precipitation strengthening and grain refinement in steel are weak. With the increase of the niobium content in the steel, the strengthening effect is enhanced, but when the niobium content is too high, the effects of precipitation strengthening and fine grain strengthening are not obvious. Accordingly, the Nb content is controlled to be 0.01 to 0.08% in the present invention.
Molybdenum Mo: molybdenum can improve the hardenability and the heat strength performance of the steel plate in the steel, so that the thick steel plate with a larger section is quenched deeply and completely quenched. Molybdenum in the steel can reduce the tendency of carbide to form a continuous network on grain boundaries, reduce residual austenite in the steel, and relatively increase the hardness and wear resistance of a steel plate matrix. Likewise, molybdenum is also a noble metal because of its high cost, and therefore, in the present invention, the Mo content is defined to be 0.1 to 0.4%.
The invention relates to a manufacturing method of a 900 MPa-level ultralow-carbon medium-manganese high-strength hot rolled steel plate, which comprises the following steps:
1) Smelting and casting
Smelting and casting into steel ingots or continuous casting billets according to the components;
2) Heating
Heating the steel ingot or the continuous casting billet at 1140-1160 ℃;
3) Rolling
Adopting a controlled rolling process, and rolling the steel ingot after cogging; or directly rolling the continuous casting blank, wherein the initial rolling temperature is 1080-1100 ℃, the thickness of the steel plate is 3-5 times of that of the finished steel plate, the temperature is kept between 850-870 ℃, and the steel plate is rolled to the thickness of the finished steel plate after the temperature is reached;
4) Cooling
Adopting a controlled cooling process, and performing online water cooling on the rolled steel plate to A 1 The temperature is 20-30 ℃ above, and the lower line is directly piled and cooled to the room temperature.
The manufacturing method of the 900 MPa-level ultra-low carbon medium manganese high-strength hot rolled steel plate comprises the following steps:
1. manganese plays an important role in the slow cooling process after water cooling.
Firstly, the diffusion of elements such as manganese, aluminum and the like in steel can still be effectively diffused due to higher temperature in the early stage of stack cooling, and the elements can be continuously enriched to the austenite which is not transformed around ferrite grains through back diffusion in the process of large nucleation of the proeutectoid ferrite grains, so that the content of alloy elements such as carbon, manganese and the like in the austenite is improved, the stability of supercooled austenite is improved, and the bainite transformation temperature is reduced;
secondly, in the latter half of the stack cooling (the temperature is reduced to below 400 ℃), austenite in the steel is subjected to bainite transformation, and manganese is not diffused basically in the process, so that the manganese content in the bainite lath is higher than the average manganese content originally designed in the steel, the effect of solid solution strengthening is achieved, and the refined bainite lath is adopted, so that the strength of the steel is obviously improved. In the bainite transformation process, although other alloy elements cannot be diffused, carbon atoms are still diffused at the stage due to smaller atoms, the bainite is formed with a carbon discharging process, at the moment, the carbon atoms further enrich carbon in the non-transformed austenite at a phase interface, the stability of the austenite is improved, the critical transformation temperature of the austenite is reduced below room temperature, and a small amount of residual austenite exists in the final steel.
2. According to the invention, the steel plate is rolled by adopting two stages, wherein the first stage rolling refines austenite grains through austenite dynamic recrystallization due to higher temperature, the second stage rolling is in a non-recrystallization temperature range, the deformation degree of the austenite grains is improved through large deformation, the defect density in a tissue is increased, rolling defects such as dislocation vacancies and the like become nucleation points of ferrite nucleation, the nucleation position of ferrite in the cooled steel is increased, and the steel plate is cooled to A in the follow-up process 1 The formation of refined ferrite grains in the heap cooling process at temperatures above 20-30 ℃ provides an advantageous tissue guarantee.
3. For the steel plate rolled to the thickness of the finished product, water cooling is carried out on line to A 1 The wire is cooled to room temperature at 20-30 ℃ above the temperature, which is one of the core technologies of the invention. Mainly in order to improve the supercooling degree of deformed austenite, the driving force of ferrite nucleation is further increased, ferrite grains are refined, and the yield strength of the finished steel plate is improved. For piling coolingIn order to control the ferrite content in the steel by reducing the cooling speed, the element such as C, mn is back-diffused to the austenite in the process of forming large ferrite grain nuclei, and the stability of supercooled austenite is further improved. The bainite transformation temperature of the element enriched austenite moves to a low temperature region due to the improvement of stability in the subsequent slow cooling process, and the supercooling degree of the austenite is increased. When the bainite transformation is performed in a low temperature region, the nucleation rate of the bainite transformation can be remarkably improved due to the large supercooling degree, the size of a bainite lath can be remarkably thinned due to the increase of nucleation positions, and the final strength performance of the steel plate can be improved due to the thinned lath size according to the calculation result of a Hall-type formula.
4. As the microstructure of the steel plate is 10-15% of fine-grained ferrite, 80-85% of lath bainite and a small amount of residual austenite, the ferrite is firstly yielded as a soft phase in the deformation process, so that the yield strength of the steel plate is lower. With the further occurrence of random deformation, bainite in the steel is deformed in cooperation with ferrite which is first yielded, and the strength of the steel plate is continuously improved. When the deformation reaches a certain degree and local stress concentration occurs, residual austenite in the steel relieves the local stress concentration through the action of transformation induced plasticity, and the capability of the steel plate for continuing deformation is improved. Meanwhile, martensite is obtained after the transformation of the residual austenite, and has relatively high carbon and manganese contents and high strength, so that the final breaking strength of the steel plate is improved. In conclusion, the structure collocation can effectively reduce the yield ratio of the steel plate, improve the deformability of the steel plate, and improve the safety performance of the building structure and engineering machinery in resisting deformation.
Compared with the prior art, the invention has the advantages that:
1. according to the invention, through reasonably designing chemical components, the use amount of noble metal elements such as chromium, nickel, molybdenum and the like is reduced by adding manganese element in the traditional low-carbon alloy steel. Reverse diffusion is carried out by utilizing the chemical concentration gradient of austenite stabilizing elements such as C, mn and the like between ferrite and austenite, so that the chemical stability and mechanical stability of supercooled austenite are improved, and the bainite transformation temperature is reduced.
Compared withIn other medium-high manganese steel products on the market at present, the addition amount of manganese element in the steel is obviously reduced, the utilization rate of Mn element is effectively improved mainly through the back diffusion effect of the element, and the alloy cost of the steel plate is reduced. The critical transition temperature of the steel plate can be obviously reduced by mutually limiting the C, mn elements, so that the microstructure can be thinned; on the other hand make A of steel plate 1 And A 3 The temperature interval between the two is enlarged, and the feasibility of on-site production is improved.
2. The prior rolling and cooling control technology adopted in medium plate products mostly adopts a forced cooling technology in a cooling stage, the steel plate is directly cooled to room temperature or 400-500 ℃, the cooling interval is larger, the forced cooling speed is higher in dependence and requirement on the cooling capacity of equipment, and then the strength and toughness level of the steel plate are improved by matching with heat treatment technologies such as tempering or tempering.
The control cooling technology adopted by the invention is to lead the steel plate to be on-line changed from A 3 Cooling the vicinity to A 1 The temperature is 20-30 ℃ above, the cooling interval is smaller, and the requirement on the cooling capacity of the cooling equipment is low. The subsequent adoption of a stack cooling system eliminates the need for off-line heat treatment of the steel plate, thereby remarkably reducing the energy consumption in the production and manufacturing process and greatly reducing the production and manufacturing cost. Meanwhile, the steel plate is directly lifted to a cold stacking area after being cooled down, so that the cooling bed field is not occupied, and the production efficiency of the rolling mill production line is improved.
3. Most of the prior medium-thickness plate high-strength steel products or the alloy components are complicated in design, so that the cost is too high; or off-line quenching and tempering is adopted in the production process, so that the production procedures are increased, and the production cost is increased; or the combination of the final products (strength, toughness and yield ratio) is poor, so that the user can only go back to the second when selecting the products.
The 900 MPa-level ultralow-carbon medium-manganese high-strength hot rolled steel plate has high strength and excellent plasticity and toughness, and through reasonable structure proportion, the yield ratio of the steel plate is effectively reduced, the deformation resistance of the steel plate is improved, and the safety of the service process is improved.
Detailed Description
The present invention will be further described with reference to the following examples, but the present invention is not limited to the following examples, and various technical solutions according to the present invention should fall within the scope of the present invention.
The components of the present invention are shown in Table 1, the process parameters of the present invention are shown in Table 2, and the performance parameters of the steel of the present invention are shown in Table 3.
The manufacturing process of the embodiment of the invention comprises the following steps: smelting by adopting an electric furnace or a converter, and casting into steel ingots or continuous casting billets; heating the steel ingot or the plate blank to 1150 ℃, rolling the steel plate at 1100 ℃ until the thickness of the steel plate is 3-4 times of the thickness of the finished product, and starting rolling at the next stage when the temperature is between 850 and 870 ℃; immediately performing online water cooling to A after the steel plate is rolled to the thickness of a finished product 1 The temperature is 20-30 ℃ above, and the reactor is cooled to room temperature.
Table 1 units: weight percent
TABLE 2
TABLE 3 Table 3
As can be seen from tables 1 to 3, the yield strength of the ultralow-carbon medium-manganese high-strength steel plate produced by the production method can reach more than 880MPa, the tensile strength reaches more than 1200MPa, and the elongation after fracture exceeds 16%.
According to the invention, through reasonable components and process design, the microstructure of the steel plate is 10-15% of fine grain ferrite, 80-85% of lath bainite and a small amount of residual austenite at room temperature, and the ratio of soft and hard phase structures ensures that the yield ratio is less than 0.75, so that the steel plate has excellent plastic deformation capability, and can meet the requirements of cutting, bending and other processes required by conventional processing; the V-shaped Charpy impact energy reaches more than 60J at room temperature, and has good impact resistance.
In summary, the 900 MPa-level ultralow-carbon medium-manganese high-strength hot rolled steel plate has obvious cost advantage, simple production process and good mechanical property.
Claims (5)
1. A900 MPa-level ultra-low carbon medium-manganese high-strength hot rolled steel plate comprises the following chemical components in percentage by weight: c: 0.06-0.12%, si:0.6 to 1.6 percent, mn: 4-6%, al:0 to 0.2 percent, P is less than 0.01 percent, S is less than 0.002 percent, nb:0.01 to 0.08 percent, ti:0.05 to 0.15 percent, mo:0.1 to 0.4 percent, and the balance of Fe and other unavoidable impurities, and the requirements are as follows:
when C is less than or equal to 0.1 percent, mn:4 to 6 percent;
when C is more than 0.1%, mn is less than or equal to 5%.
2. The 900 MPa-level ultra-low carbon medium manganese high strength hot rolled steel sheet according to claim 1, wherein the balance is Fe and other unavoidable impurities.
3. The 900 MPa-level ultra-low carbon medium manganese high strength hot rolled steel sheet according to claim 1 or 2, wherein the microstructure of the hot rolled steel sheet is 10 to 15% fine grain ferrite +80 to 85% lath bainite + a small amount of retained austenite.
4. The 900 MPa-level ultralow-carbon medium-manganese high-strength hot-rolled steel plate according to claim 1, 2 or 3, wherein the yield strength of the hot-rolled steel plate at room temperature is more than or equal to 880MPa, the tensile strength is more than or equal to 1200MPa, the yield ratio is less than 0.75, the elongation is more than 16%, and the Charpy impact energy at room temperature is more than or equal to 60J.
5. The method for manufacturing 900 MPa-level ultra-low carbon medium manganese high strength hot rolled steel sheet according to claim 1 or 2 or 3 or 4, comprising the steps of:
1) Smelting and casting
Smelting and casting into a slab according to claim 1 or 2;
2) Heating
Heating the plate blank to 1140-1160 ℃;
3) Rolling
Adopting a controlled rolling process, and rolling the steel ingot after cogging; or directly rolling the continuous casting blank, wherein the initial rolling temperature is 1080-1100 ℃, the thickness of the steel plate is 3-5 times of that of the finished steel plate, the temperature is kept between 850-870 ℃, and the steel plate is rolled to the thickness of the finished steel plate after the temperature is reached;
4) Cooling
Adopting a controlled cooling process, and performing online water cooling on the rolled steel plate to A 1 The temperature is 20-30 ℃ above, and the lower line is directly piled and cooled to the room temperature.
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